Timing Advance question

[MStefak]

When tuning the timing advance the objective is to get as much timing as possible without KR correct ?

The reason I ask is because it seems like my motor is taking a ton of timing. It has zero knock retard even under a quick WOT blip.

Just making sure im not doing anything wrong

[KLUG'S SS]

Definately not the case in the theory of keep adding timing until you get KR.

For example you may be making your best power/torque around say 22-24 degrees but your motor may take up to as high as 28-30 degrees with no knock yet but somewhere along the way you may have hit a wall and arent making any more power and you may be even losing some even though you have no KR.

This is where a good load bearing dyno sure comes into play.

[MStefak]

Thats what I figured, thanks

[rel3rd]

Definately not the case in the theory of keep adding timing until you get KR.

For example you may be making your best power/torque around say 22-24 degrees but your motor may take up to as high as 28-30 degrees with no knock yet but somewhere along the way you may have hit a wall and arent making any more power and you may be even losing some even though you have no KR.

This is where a good load bearing dyno sure comes into play.

You are referring to TOTAL TIMING @ WOT though, correct?
Not cruise, or low load, low rpm driving, I assume.

[MStefak]

So I can tune it this way ? Add spark till knock then back off a few degrees for High Octane tables, then drop a few more degrees for the Low Octane ?

WOT is a different tuning technique ?

[rel3rd]

So I can tune it this way ? Add spark till knock then back off a few degrees for High Octane tables, then drop a few more degrees for the Low Octane ?

WOT is a different tuning technique ?

I believe what KLUG'S SS is referring to is your "total timing" target. If you take a datalog of a typical NORMAL driving day, you'll see logged timing numbers of much higher than 22-24 or even 28-30 like KLUG'S SS mentioned. You'll see that in most any low load sections of the datalogs, because you can run much higher timing at low load/low rpm...even a conservative factory tune will command much higher than 20-something degrees, but we're talking LOW LOAD situations.

WOT is definitely a different scenario, because now you're talking HIGH LOAD/Mid to High RPM on the same engine.

Say you're going down the road at steady level road 65mph....i.e. Low load
You are datalogging 35 degrees timing, maybe a few more. (just throwing that number out there)
You come to a long steady downhill and coast...
Not unusual to see as high as 50+ degrees of timing in that moment.

Hopefully, I'm explaining it OK.

You'll notice in probably any stock High Octane timing table that at any given RPM, the commanded timing goes lower, as the engine load goes higher.

My truck's stock tune, which is hardly a performance tune is an example.
At a very low load (cylinder airmass) area of 0.16 g/cyl. @ 2800 RPM, the commanded timing is 45 degrees,
BUT,
at a much higher load area of 0.72 g/cyl. at the same 2800 rpm's, it is only commanding 13 degrees

In a nutshell...
Pretend your vehicle loves 20 degrees total timing at WOT.
If you made the whole high octane timing table 45 degrees, at some point it's going to detonate/knock/shatter a piston, whatever
If you made the entire table 20 degrees, it's a safe bet to say it will never detonate, but it's also a safe bet that at pretty much anywhere other than WOT, the car will be a slow, un-responsive, gas eating, turd...

Generally speaking, your vehicle may love 45 or even 50 degrees timing, at the top of the octane table graph, and it may run it's best at 25 degrees @ WOT, so you'll have to blend, or interpolate, the timing tables to take advantage of both the WOT sweet spot, and the low rpm/low load areas.

Does that make sense?

[KLUG'S SS]

Yes in my post above I was referring to WOT areas. Of course what I was stating above goes the same for part throttle regions as well in that a good load bearing dyno is also best for finding MBT with good steady state conditions.

[MStefak]

MAkes perfect sense

[rel3rd]

Yes in my post above I was referring to WOT areas. Of course what I was stating above goes the same for part throttle regions as well in that a good load bearing dyno is also best for finding MBT with good steady state conditions.

I was sure that was what you meant. I just sensed that MStefak may have been slightly confused about the total numbers. Thanks again.

[MStefak]

That I was but I think we are good now, thanks guys.